Connections in medium-voltage underground power distribution systems, such as between cables and transformers, are generally accomplished with specially designed separable male and female electrical connectors, such as loadbreak connectors and deadbreak connectors. Loadbreak cable connectors, used in conjunction with 15, 25 and 35 kV systems, generally include a power cable elbow connector and a loadbreak bushing insert. The elbow connector has one end adapted for receiving a power cable and another end adapted for receiving an insertion end of the loadbreak bushing insert. The opposite end of the bushing insert, which extends outward from the elbow connector, may in turn be received in a bushing well of a transformer, for example.
Such loadbreak elbows typically comprise a conductor surrounded by a semiconducting layer and an insulating layer, all encased in a semiconductive outer shield. The end of the elbow adapted for receiving the bushing insert generally includes a conically tapered inner surface, which mates with a conically tapered outer surface formed on the insertion end of the bushing insert. When connected with a bushing insert, the conductor encased in the elbow makes mechanical and electrical contact with a conductor encased in the bushing insert. The elbow may further include a cuff at its bushing receiving end for providing an interference fit with a molded flange on the bushing insert. This interference fit between the elbow cuff and the bushing insert provides a moisture and dust seal therebetween.
Power distribution service personnel, whose function is to monitor and control such underground power distribution systems, often need to access the cables and connectors to facilitate servicing and repairs. One of the first steps required in servicing underground cable systems is the identification (e.g., phase A or phase B) of one cable from another as it traverses underground from manhole to manhole. One way of identifying cables is to inject a signal voltage onto a cable at one location and then detect the signal on the same cable at another location.
However, this procedure requires de-energization of the power distribution system, separation of electrical connectors and installation of devices for transmitting and receiving tracing signals. Obviously, this conventional procedure results in undesirable long system outage time.
Accordingly, it would be advantageous to inject a signal voltage onto the conductor of an underground power distribution cable at one location and detect the signal at another location for communications, monitoring and control, without having to de-energize the cable or separate the electrical connectors. It would also be desirable to provide a component that permits such signal transmission and detection, which can be installed in existing field installed connection arrangements.